In general, a washing machine is a device for washing laundry by repeatedly performing operations such as washing, rinsing, and the like. The washing machine includes a main body constituting an external appearance, a storage tub installed in the interior of the main body to store water, and a rotary tub rotatably installed in the interior of the storage tub. The laundry and washing water are put together with a detergent into the rotary tub, and the rotary tub is rotated to apply a physical impact to the laundry to wash the laundry. A washing machine in which a rotational axis of the rotary tub is horizontal is generally called a drum type washing machine.
As shown in FIG. 1, the drum type washing machine includes a main body 1 forming an external appearance, a tub 2 installed in the interior of the main body 1, a drum 3 rotatably installed at an inner side of the tub 2, accommodating the laundry and washing water, and rotating them, a motor 4 for rotating the drum, a spring 5 and a damper 6 for damping vibration and an impact transferred to the tub 2, and a door 7 for opening and closing the interior of the main body. A lift 3a mounted on an inner side of the drum 2 rotates the laundry loaded in the interior of the drum 3. Both upper ends of the tub 2 are connected by the spring 5, whereby the tub 2 is installed to be suspended (or caught) in the interior of the main body 1. The damper 6 is installed to hinge-connect the tub 2 and the main body 1 and damps vibration transferred from the tub 2 to the main body 1.